A referendum on constitutional revision may be called by the Parliament, the government or through a popular initiative. Before the matter is put to the vote, the Constitutional Court must review the draft text, followed by considerations in the Parliament (Article 187). This is an important safeguard to protect the proposal's substantive validity. The Constitution provides that the court’s opinion is advisory, but the questions have to be raised whether the Parliament can disregard it or if a qualified majority vote in the Parliament is needed. This could be clarified.